SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6c88100480e3a908041a9c23f34da64961c4b0cc31cb810cae9782e29736f19' 
  AND token = 'F9BVcsiCG+ph/kZwfQriZHrIQLG2QqeJWggJ6rstMZ8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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