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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b51dd09229db3d7646f02d97ee1997188f6e34a4b35e219a15ffc950ef0c0ba8' 
  AND token = '/fD5CvkJl85QVUPeihEgxzDJsg+085Z976hv8DTD89w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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