SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b821e47ed934edef257b020e583e4a6e590b42406fa784459627510637f6e39c' 
  AND token = 'PMKCz6aDw2974SI9uOPWTAo+WvEpjRV9mn058M4zA8k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00045

JSON explain

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