SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c54b23f9048755e51d7cfb6ad7fc4d7d68b2409916ae358f35be796365401f4c' 
  AND token = 'h6TJ6FxWQBnbwkPeRsXfZhUMVFuqwdbMSQ4dRlfHOHI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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