SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '751f5c2d485b37d7284f7214a772d522f6109128aa51d79a54f752842692e86e' 
  AND token = 'nFPYSjsfsZM55LNaBYJdqF45PRiYcXZ2YgAzv6w4BCE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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