SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6c3597849b73872cacbb7ab37f29b5cd0f75c7ef2ce979da585ac54d036c3bd' 
  AND token = 'UPCvK3vGV9gD1iF61eM3oU1v4QghHAkMRBMpuVhrLHg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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