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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9240ffdee6ed55b0303a520fefe1174b8bfcd6fe02cabac8316e29ca3897c799' 
  AND token = 'e8lX11rZ9QGk+erdYUTAk5gNhqzSiiVBy0ZFl7Jvy5w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}