SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c3b87a60eda67a9f9b458b2e2993123fce662559b8b94dd397573678251de81c' 
  AND token = 'qWYMT7QCcgM91uHWjZzfyNvNr0qz+2xhrfdmuagwEBY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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