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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fc8ea2dab52e4cc8b8bda99b8b91462388f5c353667f18f8718a62a8b4aa90a6' 
  AND token = 'DxZGTeR1Vn54Tq8x9/XDIt4aAXIf85cIRh9YlqxYu40=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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