SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '98f51e103a8f836459026e52c3983231caba284983c106d1a5a818e5c889774a' 
  AND token = '79Cy7YDREE3D48mGXVklmO2KCq/F4vC2xMiczrwr1pU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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