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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b7875f4dbdde7e4fa2052f03d8ba1595a894c094b341dc9fba3477994d868b92' 
  AND token = 'RoBX+G9TvMNDvWAvoksiUBOg6gw/oPo6B+MAfNiSHeQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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