SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7e3b7531fe6ffec405d1d68f94e8a1e20398bd741406a4180459785d7a1a1b28' 
  AND token = '/ejJWfn4UqTxuURoLpd5fXWlP1Nu2+WhZRAj1AAQaWE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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