SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50ca27c88eea64bad67b3dc3329ef8d19af796862639a50d59df188cb11e0943' 
  AND token = 'HDhNNc3JzF+2sRnVThiAGtQY5XImYnIxPwEJCn7XAo8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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