SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '100ecce1bde60be0d98b74fc38cc0207801b458e5087d4b32885abc6eb2cc32c' 
  AND token = 'XDFps1wXjDWGTiT+VYmuWKnFT9Jm3rh7zeRnFBv8Ez8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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