SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '12bf1817b11b1ff930fed396982aa460d0ea12916cc5b3757016b29a052a7a2c' 
  AND token = 'DxvcUXkj+vGY4Es2VbISSolwIgKjgA0OBAthQ+fGs98=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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