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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c6791eba0845628e37868136eb8667c2b5b7e9d3096c21f52bb58d4346e65842' 
  AND token = 'X/BtlSolQNg3ZLJ2LMLmyUXiHUp1ivlMuhDZkD9JUcg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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