SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81ad1fbb3cbe318d4f23425872a3b87cc4596507b982c1c0465f8e65a8072246' 
  AND token = 'GCDrSsvTt0EWccw43214oC5AXvfEYueIkgE5giCNXu4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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