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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a307e437a46e3a4fd094fb5d2f20d97877a5a6b2307c5cd51b700f9a4356f4e4' 
  AND token = 'FA0TJMC6qp2/3rD3WaP8uVAUwilRhlJOgmd//Y5ofv4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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