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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b81bcb136d1575c5f8873540a094e59d0db378c9b5b9ad4350113969517f8ec8' 
  AND token = 'poWJd2HdC8OpKHVFBJkz4M21TystJosNGDZzPtL38bk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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