SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '976c1ab8d33532ba0a6985b3940b8f18f1f8d3113405ddaa58e57b16aac0de13' 
  AND token = 'fLn+aycJFFKFg7wWM1URsIgEVcWhe3XpNTCAdlcbSu8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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