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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6e1afdfc191069b352c750e95d0c8bebebffe22391a78898a14523df12500fa' 
  AND token = '9QZFhFCoeByYsq4adpT232YqmurIHf/4iV5tRLHz79k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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