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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51c5ccdd5ad347b969a16f5d6e3e26ae501f29c2ff81cc097c39840459a6dfa6' 
  AND token = 'welyJCfekhrpdCaD9IJmDbzt9xFMA/DCDZ1oG9ctmsA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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