SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd8a3dc709e88f0796c9cd27b8fd0e8cedda938272e5391d66d0393486da10579' 
  AND token = 'Sz8vJ9WnKF16EUs8HEehFqDOsf0upRVezEQlyyL0/ko=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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