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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c4db9993911104cf802bcc54f7afffdf14ab808800143e8d3ba8c97cd7a44f85' 
  AND token = 'OK6F/lsm9JtRQLO99AJ9NFsaiSrF8ni/c0x969dqsTQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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