SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8b98b1ef84ca7ea245ef5af9a115a6813d8ac1f5e2fda34d7327387bf6f8965' 
  AND token = 'JJxwpngMFxAt0G6Yy/9cBEScg5p2cCWbfF5QrfyQxlE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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