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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3ffe50b3e5dd4a5a4dc9885be5bffd23a10f849fff6cda9e761ba41c71a7acf5' 
  AND token = '336FFA/T8p1HNIM/ovYD5soxRiZOSRF9ByC3vWdedsY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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