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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5b9d4317caf2007908d9b9f9b50586805009cfa5da79a14033a19a8f5ad11a58' 
  AND token = '/0ec6uoMCJjRkbAiPATqRIL3Nwn+JqyVKF8SZRqvaeI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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