SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3673adc57ba9006d29944672d7a7b52bfb4c881179575d12304fd893c052215f' 
  AND token = 'qm8qKw35vcMmroyjQkSD3o3/T2GtdezMiKWPsMel1H4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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