SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8511c76159ba45c416dba657f8f0591affaca15defc088222f2e1498fe29abfb' 
  AND token = 'SEG2VwglUZtD5IiQk+yHB+dAsyuMQczMeAxw2XdxYM0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

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