SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55dc892f3f5135525e480bd15466af4d8f11525d2cbdb4a2b2efd9d9bddcf537' 
  AND token = 'qe/MVA9CBy1kWZ0yspiGyS/HWts9XSAAzgmWAaEf/w4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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