SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c57af516082cddc7ae79e000e764f632ca1b350bcadd5d355126895211e7ef74' 
  AND token = '/y5OiKuaTF8thCSJwNrYKABBeCCgUz3jBa+WyPJGYVU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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