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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3c8f15d1d43d0c0a1f899ed912a977479fa2e2672f27d7584a2d56bbf4af4c14' 
  AND token = 'jQyFGTk97xal8oMFb9EHc1/ZdaG687LozPqmeggqIS4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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