SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe3b28f6895fab9f6a9b868fe00a14c5c63acbf74d3542dd403427a2d03bf321' 
  AND token = 'VvIJBufoR8n2eCVBSIVWLE9LMJVmjinXeWMALjNRSK8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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