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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b99861136ff7753ed3cac2a53773ff5ed4154036bf0ebeeb2be80b4cde15db66' 
  AND token = 't1SCVEHVAUT1FcxiwrY6wwWIwTQwbmlPkDtBmrNMGDI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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