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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a7c8c21686758b7d087d4f66a1a0c93617a26a37ab9f2d99081d2e126f63a379' 
  AND token = '7Qa2jtNk6MJvi+zfc9ROr4MsHYjuJWlS0zEmxOMZeHo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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