SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15545bb6c03dc546894f50ab05602dd07f70a31e7ae2bdeadd3b86a7cfa814d4' 
  AND token = 'D+JNaMAsyFWKaJmfEg27fOPbtlwMUQ3kMGe8u7gfkWE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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