SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8639f2f6bb27c871f4b6c7282fe5e4a66e8586f40f073eb2e093abbbb46157f7' 
  AND token = '/g1r5HHjGXRpOBhMc5X72nh+xrwhCvVxqBBDG5Tnnt4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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