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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '251a03dc38a13d7d4304238fb958106d59c6e7b98aca8c37769ad34d406fd23a' 
  AND token = 'eQyqcChIOIqiJQDlcg2WSTTN2o/OaNc2MByghI2gjIE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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