SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b1b2c704100f266b83818d966ef133c271f56496cfe6bd37a9da403ea5295cc9' 
  AND token = 'p9CKIvdJb3UFTRtoOb4P9lGDiBzMd+xBCFZjf8KobKo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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