SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '42fb3d129edbd074dab34b623255f9573e32aaa41cb03b0bf7fc44f33e99d562' 
  AND token = 'zrShNtvBZOl7Q9vq8xs5DOUReh7HKnFDTAeofiinE/g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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