SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3439f9bdc60660d0522248b6062c902c59354aadaa3d15b39e94f987102438b6' 
  AND token = 'ZZE37W6gRvg89/ysgjAYMnryyVSKqd6203b6aZpoXu8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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