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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '350f4994ddc277176b7447c3577c427c38069c32cad425ade0ef42baa91429c9' 
  AND token = '1n8UB6ykwt3rT63h8LgQn3MT3WSpmCjWLME32isPC3E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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