SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3e020a44b88fb0385ec5c105f9f21f6a865c749c0af8d42a842a819c61393bd' 
  AND token = 'PfCoPPPRJF6yNQKIyb6aaO9pVd1rZSGxMpktTtlf/Ak=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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