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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4ca9d8ba3cf54e836224f45e4832489e8bac37c7a3463988b17fa32f7a47deb' 
  AND token = '5u4kXKj5k+Z1rAI/5DSZNGun9BMm0oLYd/Ipj2VuT9c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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