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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '18dbb8fe25812054d3a1a9186896f73dbee048f325993e216e1a9eb3c29d4c18' 
  AND token = 'wLAhUH9dh7/rkMkTgZaUPnhNt36hmW5jysghzQunX0c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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