SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b19b5e00e3dfbce220228984afec8406acf9d51dde014a176c52a2e0c0a8d434' 
  AND token = 'qvu+MJXnUfgqdE6SrTiEXtnVzAibRzbq8F16EEHBBg0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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