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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ff8993aeda14ed72b65f6c0fe31788276cddb72b8b3bfe05a7903bfb324ffcba' 
  AND token = 'zcKRN8cQiERg+6Ne+89S7Lbm20kbLrS1HKBs+SB+5Jc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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