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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '20b39f3ce4606c38d1420d76d24b90725dbe8eca94cfa91b2cdca4064370fec4' 
  AND token = '12d0gBQG9L0N4Wa/XhyTEbh/V+Sg+qIkj4WIFsLWtG4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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