SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b1f463c037feb072e667f9819288f1b66af4d4a5739bdca6d71e0cb6b378d0a' 
  AND token = 'QT/Zr8scYmcaIjXkv/IRJDFGSwLHgRSYB6IDVPR4V/Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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