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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dc9357af10d8cd868465f273bec80c2edc0b7d1f6ce5da9a4df2bfe56bf092b4' 
  AND token = 'ETZ3bNv3vRgp1aeUQewwW7YZ/+ZwdoHGw6GVcv103Bg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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