SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9846238851d7541647661917ac1b2e078720d22abf8237adda1383a3748a1c24' 
  AND token = 'r8eju5YKpgHgr/jThQ/zLcGG6Kb+jsN/PxHUa9lQu+o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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