SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e2f1c5a1cf7c19e1cc383dbe2404f9644d0923d9501b25084331936d2ba78c1a' 
  AND token = 'MPuQfW6QVrYWnI/pvt+QVg4tvwG6sZUN5SHsOTFwjjI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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