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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e99b501e5155c12d06a61a06ad3712b03dd0e8a759e6a412cc691ca1354fb830' 
  AND token = 'QMs/1a0O+ak0L4UCLcvWWuXcOLrYgkkWQGsuN3A/Ih8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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