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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4d6be2a127228273120f55d37b94240ad82956bad8ed75bc696114605ba238db' 
  AND token = 'JuCZSg4k056QiWIsg/Osh769PbWsMe9XIEZwb4d7E9A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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