SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a46a9ed50400861217d21506a5ea3779e2604a95f7d41285913f2b03ac5f939c' 
  AND token = 'adSxR7BRfyKLrlXRqD6CSpkKyssrXzj/OPItnoqAH0g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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