SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '344a5684590990d17775eec3e4db34980aa0325148db379dc683cf2dddffc8da' 
  AND token = 'lGAsJPLaG1PE6txF5U3lop5DAEpZsPwBgiggyrGZ/+0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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