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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '275a3bd79f9cfd978b37135828332fb5cfd2eef3cde5ce135c0925e5bea9de18' 
  AND token = '7B2GI3UzLEqrvYAlGqQL0tzEJVsIEOA/Lxr+S2WDCug=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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