SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '842d398a91d5d98646ba96dd6ddab9484359b67133f79f2714aee866fd502bad' 
  AND token = 'HcWqSKGL1tskRT4RbqPrUqRPgGfPLWsFM9U7suFvGLQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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