SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3966963bf7406c0e0261ac914f2c2a9ef6da3386e768c95565bcc5c8f2440958' 
  AND token = 'ym0IeYgzlacxctDZLjp9pb3thNcmSzRxSV9u8bktw28=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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