SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4ff89f7309835f9582e6962ee003bdc7b915e864bb76c955130f52398029ac57' 
  AND token = '2teilUUpMszXtuh1tdyEuGLHchOrEQLqGY6pwSLcE30=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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