SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21fa6fdfacc96a369926abb8fa575fad877941eb51d86918f148f9baece7d167' 
  AND token = 'J5BCnUKxO1p0N0nAu15CBhUotaGqhFifQBj/68YWsAQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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