SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8a8ffd6d1bde97af8dc9680deda81af8102509188595bdbb80e4a472d30d373' 
  AND token = 'R7vgb4iPxnQCK1mbwn8KLlbjYhm1OW6q/mLAkTyVHZw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00050

JSON explain

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