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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fbe528bfb055a1e4c2eff12b31464d2de5352fbcb9465574e980c79257d13d20' 
  AND token = '/OP6AmCJKGZc6sHvgLJQZFeuHOfAPdkFyoPOt5mPgUs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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