SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f23691dcf42f246b5d989c6a44dfd08f6e35d4dd22f6939f2802247f9fc5e0a4' 
  AND token = 'NsUvwrBVNKxNFC8UB0byPxxj/ZgUV7UVRkpJiPjiYCQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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