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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '250ca3470ab2a8eb1fa1bff5572f1ec4f50fd267815bcd58496e7dc13c8c8fe1' 
  AND token = 'ON3xF4FYUtQNgSVuTVh+NFWdOQH5+j43LMEWkFwNalA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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