SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9ca48382651addadc3fade4e9d2794e3c789f0e13ca8cac941ddb63c6bf1af74' 
  AND token = 'mlBcuPWTbmaG5rO37XYIRmt1XyJO+AklIWPLwHw8RdY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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