SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '53a346a22117793492a4c914bce1a6e3a55d83529ebe26d40378d063d7b9f273' 
  AND token = '8CJ5SRP56z+YpKoZWMzR9vy5dNN+ZZ0ChVZqcZVUp54=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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