SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '38108dd21ad7b51523c7fc1abfbd191e777108f1087797629cca197da868a336' 
  AND token = 'umr7rzp8HunVMfAq0Z/bUzTYnIeLbnglBYOunlIi9j0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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