SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '42d56592f82a1ee46cafea3e272b6454b31d497c281e54b441a0a07ca8232100' 
  AND token = 'XgUfTUg3PWHwedKUHWcNOB6QnYdWTZONBZFMirLOjXk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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