SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ebfa856821d0d04474928f582164fb755c652a37f6f8c6a38be1226fb584238d' 
  AND token = 'smPxUzwnAwVgoMpbOMlmIjYGdreOitmp5CsDz/OduCY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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