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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6f4fd4ca2d4c6a715461431ebac0ce9d96b75fa56ece6213c4666300b0e83d5' 
  AND token = 'EMk/F5j1CAKH/WXT/63YMmxJN346vrxeS3f6U9pGyWU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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