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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '878620e47e41ee73ee91878a4e9729825976be46243f3e6420869e4c4668adce' 
  AND token = '3g0uZAlJurm3mEpjIwr7Z6gDRtPSGHm7vBXwTzVgRC0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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