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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'feb21d43fd3c2b32a72cf47dd1402f6f49b3e087a89d40102958909c14b196a4' 
  AND token = '6V76EXyOjbdZ6gJ+SA/mLcOFj+dUbkW0gMbe33v5VUc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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