SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5b275e5fe40c58b3a6074159e8b99d64d5ae294268b34959a08abf5e5510c423' 
  AND token = 'UxMGw7aNvMgkn9iF639a8nozSmAQqpxknJUwk/Z4IjM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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