SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '879971356a371b7784e7dea66d5b318041c1d3c6d836fdc935c04dbf3d9d5274' 
  AND token = 'XiyGQ1ChqLPXZCSmYkTSvAiNINoGEUtDtCiSZY1eKz4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00045

JSON explain

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