SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ac585799817123bd57b0596b0fc1d51f301395935691128990ed00f82dd38daf' 
  AND token = 'c8M4aBkjhHsPc2R9xtSChPFXxqIh2jRyXSsoO+xYuO4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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