SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ad8c3b1008d1b0d1ff174872342d3e2f3d09f879c186ebb225fc6accda18f51b' 
  AND token = '1Hmc6hEfsPzodI3DKfIMe/xDSmS6vUcqSdeCd8qyHh8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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