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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c321be958f38f7dca806d1f7f14421464b21607f6e1b4b71fcf397aa0fb9cb1f' 
  AND token = 'QtJbIJITmmJLNO89RNbdeLqjjusOC/rknPy45gYBr00=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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