SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '108ba0f00c68d769ae0baa969a0f2954f0062380de9caaeb3605feabb2f76696' 
  AND token = 'uL79IRqdCTvFFw1Af2K8zYt4rvaUXHxkvymegs+hnes=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00052

JSON explain

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