SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '18703c6b874c73de7f4a7fcb8a98b82d6f4d3568b3955013f1621563efbd484a' 
  AND token = 'aKwOxL3wKN/F5ZPl+YB0G8iEVvH4L5WHlgzR+X0ANBE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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