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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'eb783da6c64f4cb80be21ff5800ecf6b2824e286097816282d39accf7f19ba59' 
  AND token = 'kklB3gkcHEpfVGi4cnZD8uucYHSDXf6MCgUvjO68KiI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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