SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9b8f829070b7f88ba263ad28663d56e4436f9f242a2c98f11b6ead85347a1cdf' 
  AND token = 'MlTmYYH1pu+Sc2agfrbjGYs8pyCD7CVHJwYDlwnxOF0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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