SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21859c92a4e9a91553071eca486e4aeead553299eff40437e065cc2e1ca2a1e1' 
  AND token = 'rnwBCqNlZMQCsOoi4aNKdkM5X2RjWwVN11x/5D/hgU4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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