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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8884a7e8eeaa9b212bdceb307206a94e14889a435cb2c0d0c4a9fd37e1cc141' 
  AND token = 'zEK9/K+kj8YxkIP77y4FmwB2poKjyl7tBTPPtDQxIXg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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