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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fb8208ba7b74f1d416a640d16cce5bdd3b142657dd4d47b40fe7299421d4fbf5' 
  AND token = '28/UeK/sLL4cKPGx25Vl1Q7ugBVmCDg0s1h1RH+DX0A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}