SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8d6594880e190ef841426dec9c35060841db66297972d6f4ddfd75ebc011876' 
  AND token = 'DkwhCBz5IYDwPff6w1EAvJ/MsDOi/GFizlGRkqPDpsg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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