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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd6d78da7aadfd1977e22f073a9669e833510ee3a1a619fb52f16158b3c5c1a67' 
  AND token = 'tD+9TrCwZYcEcyUUyCfGZXLNS9eO7RjmdE8NnQYvn3U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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