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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ff7a94e89af698e0802bef97711c41ee59e3240316e27d5100960967d41f73a' 
  AND token = '4tpn88JrOVxMjkqRrRz9gjL0pnAvA2sBItoVx53xe5E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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