SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7c8d0be46445ed015b93086336785af820b16aeb315553e468af3a219523824a' 
  AND token = 'e12mr+JdggUgDnjbJVzzYkdMstyAzGu48lOugiG088A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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