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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '951af78fcc57785c46a4808c024882b0da51e4a1eefb8befb26701d07673a392' 
  AND token = 'YV9emrHCsU45OsmvsFYdZ84jK5ON1ZKZU+cJpbffVGo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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