SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3e9b20bfbc1f411fbf64513cdd08f9500876f92ed84fe13962a5db628c97bc6' 
  AND token = 'kAk7KXvaSz/BaMvbY8Fbr1H9JQ/Dr1gpC3nBc3ZNsGg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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