SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f7e4ecb7a6f46921296fc7996276ec44b564d0588fd5da4a24c197fa376ff2c' 
  AND token = 'K0XJBtAmHKS5rvWh+DHzGEGkr+acHiyCH12JO1GwgZ0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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