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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b15e81d1a87cd559628bba8ada791079d901aca83eac1c06c8a78a2ae5008241' 
  AND token = 'hrxneExGw5SExi4e8zXdJFTZhFzCEopk6PI9CwaVtU8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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