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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '851ef85791af06b6d1eb84ccd7adc46dc0c1e8aab1273e0d0cc886a164b202fc' 
  AND token = 'OBEqZbaWl0T8z0eGpiOxPnrnoXBFoQimNvJb9Wp1kyI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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